Alan Ivković

Articular cartilage repair by genetically modified bone marrow aspirate in sheep

Bone marrow presents an attractive option for the treatment of articular cartilage defects as it is readily accessible, it contains mesenchymal progenitor cells that can undergo chondrogenic differentiation and, once coagulated, it provides a natural scaffold that contains the cells within the defect. This study was performed to test whether an abbreviated ex vivo protocol using vector-laden, coagulated bone marrow aspirates for gene delivery to cartilage defects may be feasible for clinical application. Ovine autologous bone marrow was transduced with adenoviral vectors containing cDNA for green fluorescent protein or transforming growth factor (TGF)-β1. The marrow was allowed to clot forming a gene plug and implanted into partial-thickness defects created on the medial condyle. At 6 months, the quality of articular cartilage repair was evaluated using histological, biochemical and biomechanical parameters. Assessment of repair showed that the groups treated with constructs transplantation contained more cartilage-like tissue than untreated controls. Improved cartilage repair was observed in groups treated with unmodified bone marrow plugs and Ad.TGF-β1-transduced plugs, but the repaired tissue from TGF-treated defects showed significantly higher amounts of collagen II (P<0.001). The results confirmed that the proposed method is fairly straightforward technique for application in clinical settings. Genetically modified bone marrow clots are sufficient to facilitate articular cartilage repair of partial-thickness defects in vivo. Further studies should focus on selection of transgene combinations that promote more natural healing.

Arthroscopy and microfracture technique in the treatment of osteochondritis dissecans of the humeral capitellum: report of three adolescent gymnasts.

The aim of this paper is to report on three cases of symptomatic osteochondritis dissecans of the humeral capitellum in adolescent gymnasts, two females and one male. In all the cases arthroscopic surgery was performed. During arthroscopy, loose osteochondral fragments were removed, the defect was debrided and microfractures were performed. All the three patients regained the full range of motion of the affected elbow, and returned to the high-level gymnastics within a period of 5 months. At 12 months follow-up, all the three patients remained symptomless and were participating in high-level gymnastics. A combination of arthroscopy and the microfracture technique is a reliable method with excellent short-term results in the treatment of the osteochondritis dissecans of the elbow.

Regenerative medicine and tissue engineering in orthopaedic surgery.

Orthopedic surgery is going through a serious paradigm shift ; instead of simply replacing damaged tissues with prosthetic or allograft material, the aim is to regenerate them. This endeavor has generated the field of regenerative orthopaedics, an increasingly expanding area of research with hopes of providing new and better treatments for diseases and injuries affecting the musculoskeletal system. As part of this process, we are witnessing a substantial accumulation of new cellular and molecular insights into connective tissue function, coupled with emerging new concepts in stem cell biology and scaffolding technologies. Indeed, any successful strategy to regenerate musculoskeletal tissues can be portrayed as an intricate interplay between the three main constituents of the regenerative system: cells, environment and scaffolds. This review is not meant to be exhaustive and comprehensive, but aims to highlight concepts and key advances in the field of regenerative orthopaedics and tissue engineering, as well as to present current possibilities for clinical translation.Orthopedic surgery is going through a serious paradigm shift; instead of simply replacing damaged tissues with prosthetic or allograft material, the aim is to regenerate them. This endeavor has generated the field of regenerative orthopaedics, an increasingly expanding area of research with hopes of providing new and better treatments for diseases and injuries affecting the musculoskeletal system. As part of this process, we are witnessing a substantial accumulation of new cellular and molecular insights into connective tissue function, coupled with emerging new concepts in stem cell biology and scaffolding technologies. Indeed, any successful strategy to regenerate musculoskeletal tissues can be portrayed as an intricate interplay between the three main constituents of the regenerative system: cells, environment and scaffolds. This review is not meant to be exhaustive and comprehensive, but aims to highlight concepts and key advances in the field of regenerative orthopaedics and tissue engineering, as well as to present current possibilities for clinical translation.

Stress fractures of the femoral shaft in athletes: a new treatment algorithm

Background: Femoral shaft stress fractures in athletes are not common but pose a great diagnostic challenge to clinicians. Because of few clinical signs, diagnosis and treatment are often delayed. Furthermore, if not treated correctly, these fractures are well known for complications and difficulties. Objective: To develop a well structured and reproducible treatment algorithm for athletes with femoral shaft stress fractures. Methods: The proposed algorithm is carried out in four phases, each lasting three weeks, and the move to the next phase is based on the result of the tests carried out at the end of the previous phase. Over nine years, we treated seven top level athletes, aged 17–21. In all athletes, diagnosis was based on physical examination, plain radiographs, and bone scan. Results: As a result of the treatment method, all the athletes were fully engaged in athletic activity 12–18 weeks after the beginning of treatment. After completion of the treatment, the athletes were followed up for 48–96 months. During the follow up, there was no recurrence of discomfort or pain, and all the athletes eventually returned to competition level. Conclusion: These results and data available from the literature suggest that the algorithm is the optimal treatment protocol for femoral shaft stress fractures in athletes, avoiding the common complications and difficulties.

Autologous bone grafting on steroids: preliminary clinical results. A novel treatment for nonunions and segmental bone defects

Clinical management of delayed healing or nonunion of long bone fractures and segmental bone defects poses a substantial orthopaedic challenge. Surgical advances and bone tissue engineering are providing new avenues to stimulate bone growth in cases of bone loss and nonunion. The reamer-irrigator-aspirator (RIA) device allows surgeons to aspirate the medullary contents of long bones and use the progenitor-rich “flow-through” fraction in autologous bone grafting. Dexamethasone (DEX) is a synthetic steroid that has been shown to induce osteoblastic differentiation. A series of 13 patients treated with RIA bone grafting enhanced with DEX for nonunion or segmental defect was examined retrospectively to assess the quality of bony union and clinical outcomes. Despite the initial poor prognoses, promising results were achieved using this technique; and given the complexity of these cases the observed success is of great value and warrants controlled study into both standardisation of the procedure and concentration of the grafting material.

Improved Healing of Large Segmental Defects in the Rat Femur by Reverse Dynamization in the Presence of Bone Morphogenetic Protein-2

BACKGROUND Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. METHODS A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 μg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. RESULTS Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. CONCLUSIONS Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. CLINICAL RELEVANCE These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bone-healing is problematic.

Polyester type polyHIPE scaffolds with an interconnected porous structure for cartilage regeneration

Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50–170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation.

Localized pigmented villonodular synovitis of the knee: diagnostic challenge and arthroscopic treatment: a report of three cases

Abstract. The localized form of pigmented villonodular synovitis (LPVS) is a lesion characterized by focal involvement of the synovial membrane. The knee is the most commonly affected joint. We report three cases of LPVS of the knee which were not diagnosed upon clinical evaluation. The aim is to bring the attention of clinicians to this pathological entity, which is often regarded as extremely rare and is therefore not considered in the early differential diagnosis of various knee derangements. Diagnostic and therapeutic arthroscopy was performed. The lesions were completely resected and patohistological findings confirmed the diagnosis of LPVS. All of our three patients have remained asymptomatic at 8, 10, and 12-month follow-ups.

Surgical treatment of diaphyseal stress fractures of the fifth metatarsal in competitive athletes: long-term follow-up and computerized pedobarographic analysis.

BACKGROUND Proximal diaphyseal stress fractures of the fifth metatarsal are common in athletes. Conservative treatment has been shown to result in high rates of delayed union, nonunion, and refracture, so internal fixation has become the treatment of choice in competitive athletes. METHODS Twenty top-level athletes with diaphyseal stress fractures fixed with intramedullary malleolar screws were evaluated. Functional outcome was assessed by American Orthopaedic Foot and Ankle Society midfoot score. Static and dynamic maximum vertical force and peak plantar pressures were evaluated with a computerized pedobarograph. RESULTS Mean follow-up from surgery to interview was 10.3 years (range, 3.5-19.0 years). Clinical healing was 95%, and there has been one refracture (5%). The mean time from surgery to return to sport was 9 weeks (range, 5-14 weeks). Twelve athletes (60%) returned to a higher level of training, 7 (35%) to the same level, and 1 (5%) to a lower level compared with the level of training before injury. Average American Orthopaedic Foot and Ankle Society midfoot score was 93.8 (range, 85-100). During the computerized pedobarographic evaluations, 18 patients (90%) presented with varus of the metatarsus and the midfoot and 2 (10%) presented with a normal plantigrade foot. CONCLUSIONS Intramedullary malleolar screws can yield reliable and effective healing of fifth metatarsal stress fractures in athletes. Varus of the metatarsus and the midfoot were predisposing factors for stress fractures in this population of competitive athletes, and all were recommended to wear orthoses until their competitive careers were completed.

Gene therapy applications in orthopaedics.

Dear Editor, With great interest and enthusiasm, we read the article “Orthopaedic applications of gene therapy“ [1]. The authors should be congratulated for their concise yet very thorough and excellent coverage of the gene therapy applications in orthopaedics. However, it is our opinion that articular cartilage deserved more of their attention. Primarily, we think that the subsection heading “Cartilage repair” should be expanded to “Cartilage repair and regeneration”, particularly since the authors did mention “stimulation of cartilage regeneration” which implies the possibility of inducing intrinsic healing of the damaged cartilage by hyaline cartilage formation. When treating localised cartilage defects we should ask ourselves: What kind of new tissue formation inside the defect do we want to induce? Ideally we aim for articular cartilage regeneration, not repair, which would mean formation of hyaline cartilage, not fibrocartilage. Treatment options published in the literature can be roughly divided into two concepts—reparative and restorative. The end result of the first concept is fibrocartilage, and the microfracture technique is the most popular representative. In contrast, the restorative concept aims for hyaline cartilage implantation/formation and includes implantation of osteochondral plugs with perfectly organised cartilage and matrix and/or cell therapy, namely autologous chondrocyte transplantation. Anabolic factors including members of the TGF-beta superfamily, such as BMPs, have proven their potential to stimulate chondrogenesis and synthesis of cartilage-specific matrix components in animal models [2, 3]. However, those proteins have short half-lives and it is difficult to maintain adequate in situ concentrations necessary for their proper functioning. Furthermore, many proteins act intracellularly and because cells cannot normally import these proteins, they cannot be used in soluble forms. These problems are the reason why gene therapy has attracted so much attention lately. The transfer of the respective genes into the joint, possibly in combination with the supply of chondroprogenitor cells, might be an elegant method to achieve a sustained delivery of such therapeutic factors at the required location in vivo [4]. Pascher et al. [5] developed a novel ex vivo method by using coagulated bone marrow aspirate as a mean of gene delivery to cartilage. Vector-seeded and cell-seeded bone marrow clots (“gene plugs”) were found to maintain their structural integrity following extensive culture and maintained transgenic expression for several weeks. Therefore, we conclude that there is a huge potential for new tissue formation by gene therapy trandsuction of cells of different origin. Cells originating subchondrally, in combination with gene therapy, may form tissue of higher quality than is achieved with the classical microfracture technique. On the other hand, hyaline cartilage formation by gene therapy induction in combination with cell implantation (possibly on biodegradable scaffolds) might be the answer to the current limitations of cartilage treatment modalities, and may provide permanent solution for the patients. Many animal studies are currently underway to investigate gene therapy-induced cartilage regeneration of chondral and osteochondral defects, and some of these investigations can be expected to lead to clinical trials and yield answers to these open questions.